Dave Erskine, Senior Public Relations Manager for Graphics Desktop at AMD just fired this off:

We combed through their announcement to understand how it was that such a claim could be made and why there was no substantiation based on industry-standard benchmarks, similar to what AMD did with industry benchmark 3DMark 11, the latest DirectX® 11 benchmark from FutureMark.

So now I issue a challenge to our competitor: prove it, don’t just say it. Show us the substantiation. Because as it stands today, leading reviewers agree with ushere, here, here, and here that the AMD Radeon HD 6990 sits on the top as the world’s fastest graphics card.